This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Protein-protein interactions are a central part of most biological processes, and our ability to understand and engineer these fundamental contacts will enable us to rationally modify these processes, including those that are involved in cancer, infectious or neurodegenerative diseases. To generate de novo protein-protein interactions, we first focus on the design of a small number of very high affinity sidechain-target interactions, following up with the design of surrounding residues to keep the key interactions in place. Designed binders are expressed as large libraries and screened via yeast surface display and fluorescence activated cell sorting to isolate the cells displaying the highest affinity binders. After further characterization of identified binders, affinity maturation is performed to achieve high-specificity and affinity binders, and to highlight ways to further optimize our computational design approach. Current targets under investigation for the generation of novel binding partners are several virulence factors and cytokines.